The present invention relates to the use of N-arylsulfilimine compounds as catalysts in the reaction of aromatic sulfonyl chloride compounds with aromatic amines to form N-arylarylsulfonamide compounds and to novel N-arylsulfilimine compounds.
The preparation of N-arylarylsulfonamide compounds by the reaction of aromatic sulfonyl chloride compounds with aromatic amine compounds typically gives unsatisfactory results because the reaction is slow and the yields are poor. The preparation of such compounds wherein the aromatic amine compound and/or the aromatic sulfonyl chloride compound possesses one or, especially, two ortho substituents is often particularly unsatisfactory because of the steric deactivation effect and, when the substituents are electron-withdrawing, the electronic deactivation effect of ortho substituents. Pyridine, picolines, and lutidines have long been known to catalyze the reaction of many sulfonyl chloride compounds with amines to form sulfonamides. Recently, it was reported that a mixture of a pyridine base and dimethyl sulfoxide gave improved results in many instances (U.S. Pat. No. 5,177,206). Many N-arylarylsulfonamide compounds are known in the art to be valuable herbicides and methods of obtaining them more readily and in improved yields are desirable.
A number of substituted N-phenylsulfilimine compounds are known, for example from J. Org. Chem., 39, 3365-3372 (1974), and the preparation and some of the chemistry of these compounds has been reviewed in the literature, for example in Russian Chemical Reviews, 59, 819-831 (1990). Certain of these compounds have been reported to be useful intermediates for further synthesis. For example, rearrangement of such compounds having at least one unsubstituted ortho-position to obtain 2-alkylthiomethylaniline compounds has been reported in U.S. Pat. No. 4,496,765. The use of N-phenylsulfilimine compounds as catalysts for the preparation of sulfonamides has not been reported.